Maryville climate

Maryville Frost Dates and Growing Season

NOAA 1991-2020 normals for Maryville 2E, 3.2 km from Maryville, elevation 985 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Maryville 2E. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around April 19 and the first fall freeze around October 17, a growing season of about 180 days.

Median at 36°F
last April 29, first October 7
Median at 32°F
last April 19, first October 17
Median at 28°F
last April 8, first October 27

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 12May 6May 4May 1Apr 29Apr 27Apr 24Apr 20Apr 14
32°FMay 3Apr 30Apr 26Apr 22Apr 19Apr 16Apr 13Apr 9Apr 4
28°FApr 22Apr 17Apr 14Apr 11Apr 8Apr 5Apr 3Mar 31Mar 24
24°FApr 13Apr 8Apr 5Apr 2Mar 31Mar 27Mar 22Mar 17Mar 12
20°FApr 5Mar 31Mar 27Mar 23Mar 19Mar 16Mar 12Mar 8Mar 2
16°FMar 30Mar 22Mar 17Mar 14Mar 11Mar 8Mar 4Feb 28Feb 24

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 22Sep 27Oct 1Oct 4Oct 7Oct 10Oct 13Oct 16Oct 20
32°FOct 2Oct 8Oct 12Oct 15Oct 17Oct 20Oct 23Oct 26Oct 30
28°FOct 14Oct 18Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 9
24°FOct 24Oct 28Nov 1Nov 3Nov 5Nov 8Nov 11Nov 14Nov 19
20°FNov 1Nov 5Nov 8Nov 11Nov 14Nov 18Nov 21Nov 26Dec 1
16°FNov 7Nov 12Nov 17Nov 21Nov 25Nov 29Dec 2Dec 6Dec 13

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F178172167163159156151147141
32°F199192188184180177172167159
28°F222214209204200197193188181
24°F242236229224220216212207200
20°F262255249245240235228223215
16°F284275269264259254249244235

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
5,992
Cooling degree days, base 65°F
1,082
Growing degree days, base 40°F
5,732
Growing degree days, base 45°F
4,549
Growing degree days, base 50°F
3,498
Growing degree days, base 55°F
2,567
Growing degree days, base 60°F
1,760

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,27600
February1,02503
March770137
April4228138
May15372392
June15234669
July2347811
August4285745
September87118484
October36717189
November752029
December1,12101

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 3.2 km from Maryville. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00235340 (Maryville 2E). Public domain.